Embedding SMA layers in a composite structure is a promising technology to improve mechanical features, but this achievement must not come at the cost of structural integrity. The research carried out within this paper was focused on assessing the delamination behavior of hybrid composite structures, specifically, ones composed of layers of a Cu-based shape memory alloy (SMA) and a glass-fiber reinforced polymer (GFRP). Different patterns of holes cut into SMA layers of a composite material have the potential to produce topologies that can be applied for improved damping in lightweight structures. To make an initial assessment of the effects of different hole patterns on the structural integrity of the composite, the authors have designed an experimental setup intended for the application of Mode II (shear) loading to the composite samples up to the point of failure.
Application of laser cutting operations on thin sheets of Cu-Al-Mn shape memory alloys can be used for shaping, or for producing different types of holes and hole patterns within the SMA sheets. In this paper, the authors evaluate the effects of laser cutting under different process parameters on the phase and chemical composition in Cu-Al-Mn sheet samples. The effects are observed using optical and scanning electron microscopy (OM and SEM), energy-dispersive x-ray spectroscopy (EDS), and differential scanning calorimetry (DSC).
State-of-the-art research shows that an increase in relative grain size in Cu-Al-Mn SMA leads to improved damping and SME performance. Building on that knowledge, the authors of this paper seek to understand if it is possible to exploit these improvements within a Cu-Al-Mn alloy, specifically, in the form of thin sheets. A series of thermomechanical treatments were applied to as-cast ingots of a Cu-Al-Mn shape memory alloy with the goal of obtaining thin sheets characterized by a high value of relative grain size. Additionally, samples of Cu-Al-Mn sheets were subjected to tensile cycling for the purpose of SMA “training”. Through optical microscopy, the authors of this paper investigated the effects of the applied treatments on the alloy structure. Furthermore, the phase transformation and damping behavior were studied using dynamic mechanical analysis (DMA). Methodology and preliminary results are presented in this paper.
The widely used Brinson model allows through experimental data to describe the behaviour of shape-memory-alloys (SMAs) in different condition of stress and operating temperature. The chief advantage of this one-dimensional constitutive behaviour model is in accounting for the existence of two forms of martensite within the alloy, twinned and detwinned. An internal variable approach that represents the martensitic fraction is introduced by the model and divided into the stress induced components and temperature induced component. And providing a uni-axial temperature-stress diagram clearly separating the regions of the three stable phases: austenite (A), twinned martensite (MT), and detwinned martensite (MD). The complete knowledge of the Brinson model allows to estimate the SMA behaviour in different conditions and to improve it according to specific tasks. In order to apply the model it is necessary to experimentally estimate the SMA material parameters These parameters include the Young’s moduli of each phase and critical transformation stresses, phase transformation temperatures as a function of stress level and thermal expansion coefficients of both austenite and martensite, as well as recoverable strain, both initial and after the alloy has been trained. While the Brinson model has been developed and validated for NiTi based alloys, the increasing interest aimed at Cu-based SMAs, mainly for their competitive price and relatively high performance, requires a validation of its extension to these materials. The paper focuses on a specific alloy of interest, Cu-16Al-10Mn (%at.), but results can be extended to different chemical compositions. The paper explores the opportunity to use experimental methods based on monotonic loading and unloading of the Cu-Al-Mn specimens, as well as thermal cycling under both zero and non-zero stress levels to estimate the parameters mentioned above. Furthermore, its goal was to ascertain whether any specificity intrinsic to the Cu-based alloy would require changes to the parameter estimation method or introduction of new parameters to the model to fully describe its behaviour.
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